Power systems are controlled so as to not only equalize a power demand with a power generation amount at all times but also maintain voltages of various power system regions within a specified voltage range. For example, distribution system voltage control is exercised by changing tabs on a transformer (LRT or load ratio control transformer) installed at a distributing substation or by changing taps on an automatic voltage regulator (SVR or step voltage regulator) installed on a distribution line.
These voltage regulators (the LRT and the SVR) are set so that a tap change generally is made with a response time constant of several tens of seconds. Further, if a plurality of voltage regulators are installed in series on a distribution line, the response time constant of a voltage regulator installed on the far side of the distribution line (feeder) is generally set to be slower than that of a voltage regulator installed near a substation (power feeding side). This decreases the number of unnecessary operations of the voltage regulator installed on the far side of the distribution line.
As regards a distribution system used in recent years, however, an increasing number of consumers have a photovoltaic power generator PV. In such a situation, the power output of the photovoltaic power generator PV varies with weather changes to cause an abrupt voltage change in the distribution system.
However, the response time constant of a voltage regulator having a tap or other mechanical mechanism is generally slower than that of a voltage change phenomenon caused by quickly changing electrical power such as a load and photovoltaic power generator output.
As such being the case, a present control amount and control target value should preferably be determined, if possible, in consideration of predicted output changes in the photovoltaic power generator PV. To make such a determination, it is necessary to exercise proper tap control in accordance with the amount of power generated by the photovoltaic power generator PV.
In order to address the above concerns, it is important for the distribution system to predict an output change amount by properly estimating the amount of power output generated by the photovoltaic power generator PV in a substation bank, a feeder, and a switch interval unit.
The following well-known methods are used to determine and predict the electrical power output of the photovoltaic power generator PV. A method described in Non-Patent Document 1 is capable of accurately estimating the output of a photovoltaic power generator PV at an arbitrary point by using scarce information about an output measurement point of the photovoltaic power generator PV.
A method described in Patent Document 1 performs prediction by using not only a previous power generation amount of a host photovoltaic power generator PV but also the power generation amount of another photovoltaic power generator PV.
A method described in Patent Document 2 makes comparison with power generation time-series data and change patterns of another photovoltaic power generator PV, and predicts the power generation amount of the photovoltaic power generator PV based on similar data.